Preparation of cellulose ethers



Patented July 20, 1937 UNITED STATES PATENT OFFICE 2,087,549 PREPARATIONor CELLULOSE ETHERS Donald 11. Powers, Moorestown, N. J., and Louis E.Book, and Alva L. Honk, Bristol, Pa., assignors to Robin 3. HaasCompany, Philadel- Phia, P8

No Drawing. Application October 26, 1934,

Serial No. 750,128

21 Claims. (01. zoo-.152)

10 in which the etheriflcation is carried out. Furthermore, in theseprocesses it is not possible to producecellulose solutions without firstcausing the disintegration of the cellulose.

The present invention relates to a method for preparing the ethers fromundegraded or undisintegrated cellulose. In our Patent 2,009,015 grantedJuly 23, 1935, we have shown that undegraded cellulose may be dissolvedin aqueous solutions of quaternary ammonium bases. If such solutions aretreated with an etherifying agent, the corresponding ethers of celluloseare readily formed. The quaternary ammonium hydroxide serves the doublepurpose of a solvent for the cellulose and an alkaline condensing agentto bring about the reaction between the cellulose and the etherlfyingagent.

Among the quaternary ammonium hydroxides which may be used as solventand condensing agent for the preparation of cellulose ethers, are thefollowing: Trimethylethylammonium hydroxide, trimethylpropylammoniumhydroxide, trimethylbutylammonium hydroxide, trimethylamylammoniumhydroxide, trimethylhexylammonium hydroxide, trimethylbenzylammoniumhydroxide, trimethylallylammonium hydroxide,trimethyl-isobutenylammonium hydroxide, dimethyldiethylammoniumhydroxide, dimethyl dibenzylammonium hydroxide, triethylmethylammoniumhydroxide, tetraethylammonium hydroxide and triethylbenzylammoniumhydroxide. In general, any quaternary ammonium hydroxide may be usedwhich contains one or more alkyl or alkylene groups having two or morecarbon atoms, or one or more aralkyl groups.

In orderto carry out the etherification of cellulose according to ourinvention, it is not necessary that the cellulose be completelydissolved as the above mentioned quaternary ammonium hydroxides may beused under such conditions that no solution or only a part solutionoccurs, in which case they serve as basic condensing agents in place ofthe usual alkali hydroxides. However, all of the above quaternaryammonium hydroxides are capable of. d ssolv ng undisintegrated droxide,trlmethyl-p-chlorobenzylammonium hycellulose and it is usuallyadvantageous to dissolve the cellulose completely before reacting on itwith the etherifying agents.

It is well known that celluloseproducts made from undisintegratedcellulose are stronger and more resistant generally than similarproducts made from disintegrated cellulose. The same is true .of theethers made according to the present process and for this reason weprefer to use substantially pure alpha cellulose in the form of cotton,cotton linters, sulphite wood pulp or some rayon cuprammonium ,form ofregenerated cellulose, such as viscose rayon or hydrolyzed The processhowever, is also applicable to degenerated or disintegrated cellulosebecause these are more readily soluble in the quaternary ammoniumhydroxides.

However,

one of the advantages of the present process is that undisintegratedcellulose may be used, thus yielding a superior product.

Any of the usual etherifylng agents may be used in our process. In theonly a few are that in general following examples mentioned, but it isunderstood any alkyl, alkylene, aralkyl or hydroxy alkyl ester of aninorganic acid may be used. Ethylene droxyalkylating also be used ashythese etherifyoxides may agents. Among ing agents are dialkylsulphates such as dimethyl sulphate, diethyl sulphate, etc., methylchloride ides and iodides iodide can be used and ethyl chloride,

benzyl chloride, etc. Bromsuch as ethyl bromide or methyl as readily asthe chlorides listed. If a hydroxy alkyl ether is desired, ethylenechlorhydrine may be used as well as the ethylene oxide mentioned. above.

The process may be illustrated by the following examples but is notlimited to.the exact conditions or materials shown, since the inventionmay be otherwise practiced within the scope of the appended claims.

l. A solution of cellulose is'prepared by mixing 150 grams of bleachedsulfite wood pulp with R00 grams of a 35% solution oftrimethylbenzylo'nmonium hydroxide in a. steel dough mix q pp d with asteam jacket. After mixing for one hour at room temperature, thedoughy'mass is warmed to C. by

outer jacket of aqueous sodium running steam into the the mixer and 1750cc. of 4% hydroxide is slowly added. The

resulting solution is a syrupy liquid.

To 450 grams above, is added evolved by the r to warm up to of cellulosesolution prepared as slowly with constant agitation, Some heat iseaction and the mass is allowed 40 C. but no external heat is applied.After about two hours, the temperature falls to room temperature andstirring is continued for 18 hours. The reaction mass is poured into anequal volume of water in which it is almost completely Soluble. Themethyl cellulose,

0.2787 gram of material gave 0.2860 gram of.

AgI. Percent CHaO=13.55. This corresponds to 0.72 methoxyl groups to oneCeHmOs unit.

2. A solution of cellulose is prepared by mix: mg 150 grams of bleachedsulfite wood pulp with 600 grams of a solution oftrimethylbenzylammonium hydroxide in a steel dough mixer.

After stirring cold for one hour, steam is tumed into the jacket and themass is warmed to 50 for thirty minutes. Fourteen hundred cubiccentimeters of 8% trimethylbenzylammonium hydroxide solution is thenadded and mixing is continued until 'the solution is substantiallyclear.

To 415 grams of the above solution is addedslowly with constantagitation 20 grams of dimethyl sulphate and stirring is continuedwithoutthe application of external heat for three hours. The mass is allowed tostand 18 hours and then poured into 350 cc. of water. It is neutralizedwith dilute sulphuric acid whereupon agelatinous precipitate forms. Whenfiltered and dried it is a resinous solid which is insoluble in water,but dissolves readily in 4% sodium hydroxide solution to form a viscoussolution. The

methyl cellulose may be precipitated from the alkaline solution byrunning into dilute acids. Thus, films and filaments can be prepared.

Analysis by Zeisel method 0.2691 gram of material gave 0.1283 gram ofAgI. .Percent CH:O=6.2. This corresponds to 0.32 methoxyl groups to oneCsHmOs unit.

3. To 450 grams of cellulosesolution as prepared in Example #1, is addedslowly with constant agitation 51 grams of ethyl bromide. Some heat isevolved by the reaction. Stirring is continued for three hours and themass is allowed to stand 18 hours. It is then poured. into an equalvolume of water and neutralized with dilute acetic acid. The free ethylcellulose is precipitated by the addition of an equal volume of.

acetone. When dry it is a resinousmass which dissolves in water to forma viscous solution. On dryingthis solution, a tough film is obtainedwhich is soluble in water.

I Analysis by Zeiselmetfiod 0.2988 gram oi material gave 0.1372 gram 01A51. Percent C2H5O=8.8. This corresponds to 0.33 ethoxyl groups to oneCqHmOs unit.

4. A solution of cellulose is preparedby mixing 150 grams of bleachedsulfite wood pulp with one liter of'a 35% solution oftrimethylbenzylammonium hydroxide in a steeldough mixer. Alter-mixingone hour,:150 grams of diethyl sulphate is slowly added with constantagitation overa period of one hour. The temperature rises slightly butno external heat is applied. After stirring for two hours, 1500 cc. 01'water is added and mixed in to form a clear viscous solution;

The solution may be neutralized with 86?? without precipitating any orthe ethyl cellulose. The solution as prepared is a good thickeningagent. It may be dried into tough films. precipitating with alcohol adry resinous solid is obtained.

Analysis by Zeisel method 0.2787 gram of material gave 0.2189 gram oiAgI. Percent CzHsO=15.05. This corresponds to .6 ethoxyl groups to oneCoHwOs unit.

' 5. To 540 grams oi ethyl cellulose solution prepared as in Example #4is added with constant agitation 100 grams 01' 10% aqueous sodiumhydroxide solution followed by 25 grams of benzyl chloride. The mixtureis heated to 60 and stirred washed with dilute acetic acid and then withwater. The product is an ethyl benzyl cellulose insoluble in water anddilute alkali solutions, but

stirring iscontinued for 5 hours, keeping the temperature at 40-50 C. Aclear syrupy'solu- "tion is obtained from which nothi'ng precipitateswhen neutralized with acetic acid. The ethyl cellulose may be isolatedby adding two volumes of acetone.

Analysis by Zeisel method 0.4036 gram of material gave 0.2812 gram ofAgI. Percent CzHsO=13.3. This corresponds to .52 ethoxyl groups to oneCsHioOs unit.

7. A mixture of 32 grams of bleached sulfite wood pulp and 250 cc. of a40% solution of triethylbenzylammonium hydroxide is stirred tillhomogeneous and 50 grams of dimethysuiphate is slowly added withcontinued stirring. The mass to gelatinize at first, but stirring iscontinued-and the mass is heated to 90 for 4 hours and stand 18 hours.

two volumw'a solid-product is obtained waicn is insoluble in water butsoluble'in 4% sodium hydroxide solution and in acetic acid solution. I

Analysis by Zeisel method ethylbenzylammonium hydroxide is stirred tillhomogeneous and 37.8grams of benzyl chloride Water is then added o! thematerial dissolves; to-Iorm'a viscoussoiution. By precipitatingwith forthree hours. At the end of'this time a fine precipitate has formed whichis filtered and is slowly added with-continued stirring. As'thereactionproceeds, heat is evolved and the viscosity becomes less. Stirring iscontinued for 6 hours at 7 lulose is filtered and washed with water.

' 9. Fourhundred thirty-five grams of a cellulose 1 solution prepared asin Example #1 is placed in a one liter fiask equipped-with anemcientstirrer The fine precipitate of benzyl celand altub'e whichdips belowfithe sin-lace of the liquid. Through thistub'eis introduced 10 grams ofethylene oxide gas' with constant agitation.

some heat evolyed by the reaction, but no ex- 11. A cellulose solutionis prepared by mixing 162 grams of bleached sulfite wood pulp with 800cc. of a 35% solution of trimethylbenzylammonium hydroxide in a steeldough mixer. As

soon as the mixture is homogeneous 400 cc. 0!-

diethyl sulphate is added slowly over a period of three hours. Themixture is poured into alcohol, neutralized with dilute acetic acid andan equal volume of water is added. The gelatinous preprepared in ExampleNo. 1 may be mixed cipitate which forms is filtered and dried. Theproduct is only very slightly soluble in water and is insoluble in 4%sodium hydroxide solution. It dissolves in alcohol.

Analysis by Zeisel method 0.3902 gram of material gave 0.6265 gram 0AgI. Percentethoxyl =30.7. This corresponds to 1.25 ethoxyl groups toone Col-11005 unit.

12. Thirty-two grams of bleached sulphite wood pulp is dissolved in 240grams of a 35% solution of trimethylbenzylammonium hydroxide. When thesolution is homogeneous, 36 grams of Z-methylallyl chloride is slowlyadded keeping the temperature at 60. Stirring is continued six hours.The ether precipitates from solution as it forms. It is filtered andwashed with water. When dry it is insoluble in water and dilute sodiumhydroxide, but dissolves in 75% acetic acid to form a viscous syrup.

' The properties of cellulose films or filaments may be modified byadding to the cellulose dissolved in a quaternary ammonium hydroxidesolution, cellulose ethers. which are themselves soluble in thequaternary ammonium hydroxide solution. Thus, a cellulose solution suchas that with varying proportions of the methyl cellulose prepared inExample No. 2. The methyl cellulose may be added in the form of thereaction mixture in which it is prepared or the pure isolated ether maybe added. Thus, it is possible to obtain films or filaments containing amixtureoi cellulose and cellulose ether and the properties of the filmsand filaments can be largely modified by varying the proportions ofcellulose and cellulose ether used.

It should be noted that undegraded cellulose droxide may be diluted withsodium hydroxide without precipitation. It has been found that whenundisintegrated cellulose is treated with a mixture of quaternaryammonium hydroxide and sodium hydroxide that no solution occurs. It hasalso been found that when cellulose is treated with and contains sodiumhydroxide it will not dissolve in quaternary ammonium hydroxide. It isclear then that the type of solution obtained when aqueous sodiumhydroxide is added to solutions of cellulose in a quaternary ammoniumhydroxide is entirely different-and distinct from those compositionsobtained by treating cellulose with sodium hydroxide alone. It hasfurther been found that undisintegrated cellulose dissolved in aquaternary-ammonium hydroxide and diluted with sodium hydroxide reactswith alkylating agents in the. same way as cellulose dissolved inaqueous solutions of quaternary ammonium hydroxides alone.

We claim:-

l. The process of producing cellulose ethers comprising treatingcellulose with an etherifying agent in the presence of an aqueoussolution of a quaternary ammonium hydroxide.

2. The process of producing cellulose ethers comprising treating alphacellulose with an etherifying agent in the presence of an aqueoussolution 01 a quaternary ammonium hydroxide.

3. The process of producing cellulose ethers comprising dissolving alphacellulose in an aqueous solution of a quaternary ammonium hydroxide andtreating the dissolved cellulose with an etherifying agent, saidammonium hydroxide having the formula (R) aR'NOH in which each R is amethyl or ethyl group and R is a saturated or unsaturated alkyl radicalcontaining more than one and less than seven carbon atoms or an aralkylradical.

4. The process of producing cellulose ethers comprising dissolvingcellulose in an aqueous solution of a quaternary ammonium hydroxide andtreating the dissolved cellulose with an etherifying agent, saidammonium hydroxide having the formula (R)2(R')2NOH in which each R is amethyl or ethyl group and each R is a saturated and treating thedissolved cellulose with anetherifying agent.

7. The process of producing cellulose ethers comprising dissolvingcellulose in an aqueous solution of a quaternary ammonium hydroxide andtreating the dissolved cellulose with an etherifying agent, saidammonium hydroxide containing three methyl groups and an unsaturatedallphatic radical.

8. The process of producing cellulose ethers comprising dissolvingcellulose in an aqueous solution of trimethyl isobutenyl ammoniumhydroxide and treating the dissolved cellulose with an etherifyingagent. I

9. Theprocess of producing cellulose ethers comprising dissolvingcellulose in an aqueous solution of a quaternary ammonium hydroxide andtreating the dissolved cellulose with an etherifying agent, saidammonium hydroxide containing two alkyl radicals and two aralkylradicals.

10. The process oi. producing cellulose ethers comprising dissolvingcellulose in an aqueous solution of dimethyldibenzylammonium hydroxideand treating the dissolved cellulose with an etherifying agent.

11. The process of: producing cellulose ethers comprising treating alphacellulose with an containing two alkyl radicals and two aralkylradicals.

14. The process of producing cellulose ethers comprising treatingcellulose in the presence 01' an aqueous solution of 'a quaternaryammonium hydroxide with an etheriiying agent that is an ester of aninorganic acid, the alcohol radical of which has the general formulaRCHs-in which It represents hydrogen or an organic radical.

I 15. The process of producing cellulose ethers which comprises treatingcellulose in the presence 01' an aqueous solution of a quaternary amthatis an ester of an inorganic acid, the alco-v 'rnonium hydroxide with anetheriiying agent that is an aliphatic ester or an inorganic acid.

16. The process of producing cellulose ethers comprising treating alphacellulose in the presence of an aqueous solution 01 a quaternaryammonium hydroxide with an etherifying agent that is an ester oi. aninorganic acid, the alcohol radical of which has the general formula RCH2- in which R represents hydrogen or an organic radical.

17. The process of producing cellulose ethers comprising treating alphacellulose in the presence of an aqueous solution of a quaternaryammonium hydroxide with an etheriiying agent hol radical .of' which hasthe general formula R CHa-in which R represents hydrogen or an organicradical, said quaternary ammonium hy- I droxide containing at least onebenzyl substituent.

18. The process-of producing cellulose ethers which comprises treatingcellulose with an etherifying agent in the presence or an aqueoussolution oi a quaternary ammonium hydroxide having the formula (R):R'NOH in which each R is a methyl or ethyl group and R is an an]- kylradical or a saturated or unsaturated allwl radical containingmore thanone and less than seven carbon atoms.

19. The process of producing cellulose ethers which comprises treatingcellulose in the presence 01' an aqueous solution 01' a quaternary am-'monium hydroxide with an etheriiying agent that is an ester or aninorganic acid, the alcohol radical or which has the general formula RCHs-in which R. represents hydrogen or an organic radical, saidquaternary ammonium hydroxide containing at least one benzylsubstituent.

20. The process of producing cellulose ethers comprising treatingcellulose with an etheriiy-- ing agent in the presence of an aqueoussolution oi a quaternary ammonium hydroxide which contains as one of'itssubstituents a 'member of the group consisting of aliphatic groupshaving 'at least two carbon atoms and aralkyl groups.

21. The process 01' producing-cellulose ethers comprising treating alphacellulose with an etherirying agent in the presence oi'an aqueoussolution oi a quaternary ammonium hydroxide which contains as one oi'itssubstituents a member of the group consisting of aliphatic groupsgroups.

DONALD H. POWERS.

LOUIS H. BOCK. ALVA L. HOUK.

having at least two carbon atoms and aralkyl, I

